Rerun the static analysis - CAESAR II - Reference Data

CAESAR II Applications Guide

PPMProduct
CAESAR II
PPMCategory_custom
Reference Data
Version_CAESAR
12
  1. In the Classic Piping Input dialog box, click Start Run to run the Error Checker.

    Error checking should complete without any warning or error messages. The model is ready for static analysis.

    If any errors do occur, carefully read the messages and return to Classic Piping Input to correct them.

  2. Click Batch Run to run the static analysis.

    The software performs analysis for the piping system and the basic load cases.

    When complete, the Static Output Processor displays.

    The model uses the load cases created for the original model in Tutorial A. For more information, see Check the static load cases.

Review the graphical analysis results

  1. Selecting the (OPE) load case, and then click 3D Plot .

    A view of the piping system model displays.

  2. Click Deflected Shape .

    The graphics show the model and a normalized deflected shape of the system in the operating condition.

  3. To return to the Static Output Processor, close the graphics window.

Generate the static output reports

  1. Create a set of reports by selecting:

    • For Load Cases Analyzed, SHIFT-click to select the OPE, SUS, and EXP load cases

    • For Standard Reports, CTRL-click to select Displacements, Restraint Summary, and Stresses.

    • For General Computed Results, select Hanger Table W/Text

  2. For Output Viewer Wizard, click Add, and then click Finish.

    The reports display in a tabbed window.

Review the stress reports

Check the sustained stresses (shown below) and expansion stresses (not shown) to confirm that they remain below their allowable limits. The highest sustained are 2017 psi and the highest expansion stresses are 5419 psi, below the allowable stress limits. The sustained stresses increased a small amount because of the longer spans between supports while the expansion stresses show a significant reduction. The added system flexibility caused this reduction in expansion stress. That is a good indication that the nozzle loads have dropped as well.

Review the hanger report

Examine the impact of the hanger modification on the pump nozzle loads at node 5.

The software selected a heavier spring (size 12) for installation at node 28. In the original Tutorial A analysis, a size 10 spring was selected. The spring now carries 2202 pounds in its hot position. This greater load is the result of the modification to the spring hanger selection criteria where the pump is disconnected in the Y direction when the software calculates the spring’s hot load. The added load-carrying capability of the spring reduces the vertical load on the pump nozzle.

Review the restraint summary

The operating and sustained (installed) restraint summary show the impact of this model modification on the pump nozzle loads at node 5.

The pump discharge nozzle loads at node 5 look much better, showing the impact of the change in flexibility at node 40. The loop adds flexibility in the Z-direction. The Z-force on the pump falls from 747 pounds to 235 pounds. The large operating moment about the X-axis and the target of this redesign drops from almost 10,000 pounds to 2,755 pounds.

Another interesting effect of this added flexibility is the increase in the Z-moment from -300 foot-pounds to +1519 foot-pounds. The pump load in the Y-direction exhibits the adjustment to the hanger selection. The hot load on the pump is -206 pounds and the cold load on the pump is +337 pounds. If necessary, the hanger load could be adjusted to bring the pump installation load to zero or the pump operating load to zero. The spring support at node 28 now shows a hot load of 2,202 pounds and a cold load of 2,540 pounds.

By releasing the anchor in the initial weight analysis, the spring carries the riser load. This load was only 904 pounds in the original analysis. The extra flexibility also changed the support load at node 33. Originally, the support load dropped as the pipe became hot. Now, the load increases as the pipe heats up. The vessel nozzle loads at node 40 show a similar pattern of change as the pump nozzle. Most loads drop, but there is one moment (in this case it is X) that increases.

Review nozzle loads

Confirm that the discharge nozzle loads are below their maximum allowed values. Refresh discharge loads in Equipment Analysis and rerun the analysis, or refer to the original analysis to quickly locate the individual limits and compare them to the new operating loads on node 5:

Direction

API Limit

Model Results

X (lb.)

1700

136

Y (lb.)

2200

-206

Z (lb.)

1400

-235

RX (ft.lb.)

5200

-2755

RY (ft.lb.)

3800

-1540

RZ (ft.lb.)

2600

1520

For this exercise, the loading on the suction side of the pump is assumed to meet allowable loading. Two times the API allowable loading was used.

Because all six components of the discharge nozzle loads are below their limits, no additional checks (conditions F.1.2.b. and F.1.2.c.) need to be made. The discharge nozzle is no longer overloaded. The final pump evaluation cannot be made until the suction nozzle loads are compared with their API 610 limits.